fish: color variable validation function

fish/functions/fish_colors_check.fish

@@ -0,0 +1,46 @@
+function fish_colors_check --description 'Validate the fish color variables' --argument-names fish_srcdir
+    if test -z "$fish_srcdir"
+        echo "Usage: fish_colors_check <fish_srcdir>"
+        return 1
+    end
+    if not test -d "$fish_srcdir"
+        echo "Error: not a directory: $fish_srcdir"
+        return 2
+    end
+
+    set --local allcolors (string collect (rg --no-line-number --no-filename --only-matching 'fish(?:_pager)?_color[a-z_]*[a-z]+' $fish_srcdir | sort | uniq))
+    set --local setcolors (string collect (set --names | string match 'fish*_color*'))
+
+    set --local missingcolors
+    set --local unknowncolors
+
+    for color in $allcolors
+        if not contains -- $color $setcolors
+            set missingcolors $missingcolors $color
+        end
+    end
+
+    for color in $setcolors
+        if not contains -- $color $allcolors
+            set unknowncolors $unknowncolors $color
+        end
+    end
+
+    if test (count $missingcolors) -gt 0
+        # *current regex matches some invalid cases
+        #
+        # example: set -l color_name fish_color_git_$i
+        #   match:                   fish_color_git
+        echo "These color variables are (potentially*) defined, but unset:"
+        for color in $missingcolors
+            echo " - $color"
+        end
+    end
+
+    if test (count $unknowncolors) -gt 0
+        echo "These color variables are set, but undefined:"
+        for color in $unknowncolors
+            echo " - $color"
+        end
+    end
+end

fish/functions/video_compress.fish

@@ -1,6 +1,6 @@
 function video_compress --argument-names srcfile
     if test -z "$srcfile"
-        echo "Error: missing argument"
+        echo "Usage: video_compress <srcfile>"
         return 1
     end
     if not test -f "$srcfile"